The effect of salinity upon the wood-boring activity of Limnoria was investigated experimentally. Boring decreased linearly with salinity and ceased altogether below io%o. The limiting salinity varied inversely with the temperature, being 12%0 at 17-6 C and 15 %0 at 14-9 C (average temperatures). The boring activity was intensive in its early stages but after about 5 weeks fell to a lower constant rate.

Survival experiments suggested that the low salinity was the direct cause of the reduced boring activity. The only lethal salinity found during the period of the experiments (65 days) was 6%0 which proved fatal in about 15-20 days. The next higher salinity tested was i2%0. No reduction in survival was found in concentrated salinities up to a value of 48 %0, the highest salinity examined.